In typical home audio systems, the loudspeaker drivers are mounted in wooden or plastic boxes that provide acoustical isolation between the front and rear output of the driver and reinforce the speaker driver's low frequency output. In contrast, automotive sound systems typically employ a dipole speaker mounted in an infinite baffle configuration using the inside of the doors or trunk as the enclosure and rely on the vehicle sheet metal and interior trim as a baffle. A baffle isolates the sound pressure emanating from the front and rear of the speaker cone. Proper baffling is important because the sound from the front and rear of the speaker are 180 degrees out of phase and will cancel each other at lower frequencies.
Overall speaker low frequency performance in a vehicle is affected by door inner access holes, water sealing, door trim stiffness, and door trim fastener locations. It is important to know how speaker package designs compare with an ideal environment (perfect baffle). The difference in performance between an ideal environment and a vehicle environment represents the loss in baffling. The frequency range of interest is from about 40 Hz to about 200 Hz. Accordingly, it will be appreciated that it would be highly desirable to have an apparatus and method for determining loss in baffling due to the speaker environment in a vehicle being non-ideal.